Periodic crashing (in Window Maker?) on Ascii

So I just upgraded to Ascii from (Devuan) Jessie last week when some kind of snafu with updates ended up breaking the suspend functionality on my laptop. (Don't know exactly what the story was there, I just took it as a prompt to make the move.) This went fairly smoothly overall; however, I was dismayed to find that GTK3 has metastasized and taken over still more of XFCE while I wasn't looking. Accordingly, I decided to move back to my old-reliable desktop environment, Window Maker. Unfortunately, while it's mostly working as expected, I've been having problems with the system periodically kacking itself that I was not having before.

Every so often, the screen goes black except for rapid yellow noise patterns in the very leftmost pixel column while the fan revs up, presumably due to CPU activity. Ctrl-Alt-Fn does not switch to another virtual terminal, or if it does that's also hidden under blackness and noise. I haven't conducted extensive tests to see whether the system is responding at all, but the Suspend key doesn't work, so my guess is "no." Thus far, I've pretty much had to power it off manually and reboot in order to get back to normal, and that's getting a little old.

I'm not sure, but I suspect this originates in Window Maker somewhere, because it happened constantly while I was in the process of getting my dock icons and application menu set up; it's much less frequent in normal use, but still does apparently happen. However, I can't say that with certainty because I wasn't really using XFCE for that long post-upgrade, so I may simply have missed it occurring under that environment.

The laptop is a Thinkpad X201 and the distribution is Ascii-amd64 with all the latest updates. I've poked around a little in ~/.xsession-errors and /var/log/messages but I haven't noticed anything obviously relating to whatever's going on. Anything else I should look at to see if I can figure this out?

(Also, separate, minor, probably-unrelated-but-you-never-know issue: ever since the upgrade, the system comes back from suspend with xscreensaver -lock running but the screen off - the monitor doesn't actually turn on until I press a key. Any idea what's up with that?)